Field of the Invention
The present invention relates to a method of making a rotary tool formed by a powder metallurgy process for chip removing machining with at least two helically extending chip flutes. The invention also relates to a system for performing such method.
Background Information
Tools such as twist drills or end mills are generally manufactured starting from sintered cylindrical blanks in which chip flutes are ground and a shank portion without flutes is formed. Sometimes, a ground blank is subsequently attached to a cylindrical shank to form the finished tool. This is an expensive and time consuming manufacturing route. The problem has partly been solved by extrusion molding of hard metal mixed in a carrier such as disclosed in U.S. Pat. No. 4,779,440. An extruded drill blank having chip flutes of constant pitch along the circumference of the blank is obtained by heating a hard metal powder to extrusion temperature, pressing the heated powder through a space defined by a mandrel and a nozzle while rotating the blank. The blank is guided by the extrusion in direction past a helical ridge provided inside of the nozzle, to shape chip flutes along the blank. A drawback of this known technique is that the chip flutes are obtained along the entire length of the blank and, after having been cut into suitable length, has to be joined to a shank in order to provide a suitable portion of mounting in a machine tool.
Another solution is disclosed in WO 00/74870 according to which a rotary tool such as a helix drill or an end mill for example, is manufactured by forming a blank by an extrusion process. During the extrusion, a mixture is passed through a die which provides a cylindrical shape to the outer peripheral surface of the mixture. A plurality of jaws are disposed downstream of the die for conducting the mixture. Each jaw includes a helical ridge for engaging the outer surface of the extruded mass to cause a helical groove to be formed therein which constitutes a chip flute in the tool. During the extrusion, the jaws are moved away from the mixture to terminate formation of the chip grooves, and thus form a shank portion on the tool. The drawbacks of this method is that the cooling channels may be negatively affected by the formation of the flutes. One set of jaws can only produce one type of flute geometry. If a different pitch is desired a different set of jaws has to be used. The cooling channels are formed during twisting.
U.S. Pub. No. 2008/0152444 A1 also describes a method of forming flutes in a tool body as the body is extruded. The method utilizes chisels that form flutes in the relatively soft material as it is extruded prior to sintering. The chisels are retractable so that a shank portion without flutes may be formed prior to the green-body being separated from the extruding machine. While an improvement to the methods previously discussed, such method is limited as to the dimensional accuracy of the flutes formed as well as the quantity of flutes that may be formed as the material to be cut is soft at this stage and is difficult to cut with good accuracy. Furthermore, as with the methods previously discussed, such method is only applicable to extruded rods, and not to rods made by direct pressing.
Accordingly, there exists a need for improved methods for forming cutting tools and systems for carrying out such methods.